Wireless charging, also known as Wireless Power Transfer (WPT), is a technology that enables a power source to transmit electromagnetic energy to an electrical load across a gap, without interconnecting cords. Two directions for WPT are radiative wireless charging, which transfers energy via, for example, radiating electromagnetic, ultrasound, or acoustic waves and non-radiative charging, which transfers energy via an oscillating electromagnetic field.
Wireless power transmission systems can include a power transmitter unit (PTU) and power receiver unit (PRU). The transmitter can include components to supply power to a transmitter resonator coil which is coupled to a receiver resonator coil in a receiver. The receiver can be coupled to one or more loads, such as those of a mobile electronic device, medical device, vehicle, etc. It can be beneficial to have some type of communication path between the receiver and the transmitter in order to conserve efficiency.
When a PRU is associated with a device having a battery, charging that battery can put an undue burden on the distribution of heat across the PRU, due to converting the coupled voltage from the PTU over to the load, requiring the conversion of an alternating voltage to a regulated DC voltage. In particular, the voltage regulation circuitry of the PRU can be the main portion of the circuitry that dissipates heat, due to the voltage regulation circuitry dropping the voltage from a relatively high input voltage to a lower voltage when the battery is somewhat depleted. Further, during operation, the input voltage to the PRU from the PTU can vary, also potentially resulting in high power dissipation in the voltage regulation circuitry of the PRU.